Date Set For Plebiscite

It's expected to cost $122 million.

The Federal Government has outlined the date for a plebiscite to change the Marriage Act, as well a voluntary postal vote unveiled as a contingency yesterday.

The optional ballot will be invoked if Parliament rejects a compulsory plebiscite for a second time.

This is looking likely with the Greens, Labor and the Nick Xenophon Team all indicating they will once again knock back the bill, which Opposition leader Bill Shorten labelled a delaying tactic on Tuesday morning.

"We don't put issues of electricity prices or housing affordability or fairness, or Malcolm Turnbull's corporate tax cuts – he's not writing to the people asking their permission on that."

In the 2016 budget the Coalition estimated the plebiscite would cost about $160 million, while the Prime Minister told reporters on Tuesday morning that a voluntary postal plebiscite, to be conducted by the Australian Bureau of Statistics, is priced at $122 million.

Mr Turnbull said a plebiscite would be held on November 25, just before the final sitting fortnight of parliament. If it came back in the affirmative a private member's bill would then be introduced into parliament.

The result would be revealed on November 15 if an optional postal vote was held instead.

"The intention would be to have ballot papers arrive in people's letter boxes from 12th September onwards," said Mathias Cormann.